问Javascript中的递归四分位排序器
EN

Stack Overflow用户

提问于 2018-10-24 17:53:48

回答 1查看 62关注 0票数 0

我正在用Javascript构建一个四分位数的分类器。Codepen在下面。将表格中的标题拖到表格上方的灰色区域，以查看表格排序。https://codepen.io/carbondesign/pen/MPPRPW?editors=0010

这段代码工作正常，除了两个问题: 1.我写了它的长手写，以便为我自己分解问题2.按第三列排序不起作用。

要查看#2，请将" area“拖入分类框(表格上方的灰色区域)，表格将按预期进行排序(俄罗斯是最大的国家)。将" population“拖动到排序区域，表将按预期进行排序(中国是最大、人口最多的国家)。将“人口增长率”拖到分拣区，它几乎是有效的，但并不完全有效。我得到了双精度值，排序顺序应该如下所示，伊拉克是最大、人口最多、增长率最高的国家。

伊拉克2.93
埃塞俄比亚2.89
坦桑尼亚2.79
安哥拉2.77
喀麦隆H114也门2.47
尼日利亚2.45

刚果2.45

Mozambique 2.45
Afganistan 2.32H223肯尼亚1.93
阿尔及利亚1.84
埃及1.79
苏丹1.72
印度1.22
Pakistan

/code>

沙特阿拉伯1.46
Venezuela 1.39
南非1.33
土耳其1.26
伊朗1.2
墨西哥1.18
Australia 1.07
Columbia 1.04
缅甸1.01
Morrocco 1
...

有问题的代码从第154行开始(同样，我特意用手写了这段代码)：

    let thirdBuckets = [[],[],[],[]]
    secondBuckets.forEach( (secondbucket) => {
        secondbucket.forEach((currentVal) => {
            if(currentVal[sorters[i]] !== null){
                if(currentVal[sorters[i]] > columnSummary[sorters[i]].min && currentVal[sorters[i]] <= columnSummary[sorters[i]].first){
                    thirdBuckets[0].push(currentVal);
                }
                if(currentVal[sorters[i]] > columnSummary[sorters[i]].first && currentVal[sorters[i]] <= columnSummary[sorters[i]].mean){
                    thirdBuckets[1].push(currentVal);
                }
                if(currentVal[sorters[i]] > columnSummary[sorters[i]].mean && currentVal[sorters[i]] <= columnSummary[sorters[i]].third){
                    thirdBuckets[2].push(currentVal);
                }
                if(currentVal[sorters[i]] > columnSummary[sorters[i]].third && currentVal[sorters[i]] <= columnSummary[sorters[i]].max){
                    thirdBuckets[3].push(currentVal);
                }
            }else{
                nullBucket.push(currentVal);
            }
        });
        secondbucket.length = 0;
        thirdBuckets.forEach((thirdbucket) => {
            thirdbucket.forEach((currentVal) => {
                secondbucket.push(currentVal)
            })
        });

    })
    console.log(thirdBuckets);
    results.length = 0;
    secondBuckets.forEach((secondbucket) => {
        // regularSort(secondbucket, sorters[i])
        secondbucket.forEach((currentVal) => {
                results.push(currentVal)
        })
    })
}

感谢所有的建议。

javascript

arrays

recursion

quartile

回答 1

Stack Overflow用户

发布于 2018-10-25 03:58:34

给定一个排序方法数组：

[ (a, b) -> n ]

您可以通过迭代这些方法并应用它们，直到第一个方法返回-1或1，从而创建组合排序方法。您可以使用递归来完成此操作，但在简单的循环中会更容易：

// Using recursion
const chainSortRec = ([s = Done, ...sorters]) => 
  (a, b) => s === Done 
    ? 0 
    : s(a, b) || chainSortRec(sorters)(a, b);

// Using a regular loop
const chainSort = (sorters) => (a, b) => {
  for (let i = 0; i < sorters.length; i += 1) {
   const res = sorters[i](a, b);
   if (res) return res;
  }    
  return 0;
};

下面是一个基于多个排序器对一组数组进行排序的示例：

const numSort = (a, b) => a > b ? -1 : a < b ? 1 : 0;

const sortBy0 = ([a  ], [b  ]) => numSort(a, b);
const sortBy1 = ([,a ], [,b ]) => numSort(a, b);
const sortBy2 = ([,,a], [,,b]) => numSort(a, b);

const Done = Symbol();

// Applies the first sort method, if any.
// If it returns 0, it recurses to the next.
// When out of sort methods, it returns 0.
const chainSortRec = ([s = Done, ...sorters]) => 
  (a, b) => s === Done 
    ? 0 
    : s(a, b) || chainSortRec(sorters)(a, b);

const data = [
  [2, 0, 0],
  [1, 0, 0],
  [1, 1, 1],
  [1, 1, 0],
  [3, 0, 0],
];

console.log(
  data
    .sort(chainSortRec([sortBy0, sortBy1, sortBy2]))
    .map(xs => `[ ${xs} ]`)
    .join("\n")
);

这可能只是部分地回答了你的问题，但我花了很长时间来检查你的所有代码行以及与UI代码的混合……

无论如何，这里有一个完整的运行控制台示例，其中包含许多注释，它们给出了您所需的结果：

/*
* 提示：该行代码过长，系统自动注释不进行高亮。一键复制会移除系统注释 
* const data = [{"name":"Afghanistan","area":652230,"population":32564342,"populationGrowthRate":2.32},{"name":"Akrotiri","area":123,"population":null,"populationGrowthRate":null},{"name":"Albania","area":28748,"population":3029278,"populationGrowthRate":0.3},{"name":"Algeria","area":2381741,"population":39542166,"populationGrowthRate":1.84},{"name":"American Samoa","area":199,"population":54343,"populationGrowthRate":-0.3},{"name":"Andorra","area":468,"population":85580,"populationGrowthRate":0.12},{"name":"Angola","area":1246700,"population":19625353,"populationGrowthRate":2.77},{"name":"Anguilla","area":91,"population":16418,"populationGrowthRate":2.03},{"name":"Antarctica","area":null,"population":null,"populationGrowthRate":null},{"name":"Antigua and Barbuda","area":443,"population":92436,"populationGrowthRate":1.24},{"name":"Argentina","area":2780400,"population":43431886,"populationGrowthRate":0.93},{"name":"Armenia","area":29743,"population":3056382,"populationGrowthRate":-0.15},{"name":"Aruba","area":180,"population":112162,"populationGrowthRate":1.33},{"name":"Ashmore and Cartier Islands","area":5,"population":null,"populationGrowthRate":null},{"name":"Australia","area":7741220,"population":22751014,"populationGrowthRate":1.07},{"name":"Austria","area":83871,"population":8665550,"populationGrowthRate":0.55},{"name":"Azerbaijan","area":86600,"population":9780780,"populationGrowthRate":0.96},{"name":"Bahamas The","area":13880,"population":324597,"populationGrowthRate":0.84},{"name":"Bahrain","area":760,"population":1346613,"populationGrowthRate":2.41},{"name":"Bangladesh","area":143998,"population":168957745,"populationGrowthRate":1.6},{"name":"Barbados","area":430,"population":290604,"populationGrowthRate":0.31},{"name":"Belarus","area":207600,"population":9589689,"populationGrowthRate":-0.2},{"name":"Belgium","area":30528,"population":11323973,"populationGrowthRate":0.76},{"name":"Belize","area":22966,"population":347369,"populationGrowthRate":1.87},{"name":"Benin","area":112622,"population":10448647,"populationGrowthRate":2.78},{"name":"Bermuda","area":54,"population":70196,"populationGrowthRate":0.5},{"name":"Bhutan","area":38394,"population":741919,"populationGrowthRate":1.11},{"name":"Bolivia","area":1098581,"population":10800882,"populationGrowthRate":1.56},{"name":"Bosnia and Herzegovina","area":51197,"population":3867055,"populationGrowthRate":-0.13},{"name":"Botswana","area":581730,"population":2182719,"populationGrowthRate":1.21},{"name":"Bouvet Island","area":49,"population":null,"populationGrowthRate":null},{"name":"Brazil","area":8514877,"population":204259812,"populationGrowthRate":0.77},{"name":"British Indian Ocean Territory","area":54400,"population":null,"populationGrowthRate":null},{"name":"British Virgin Islands","area":151,"population":33454,"populationGrowthRate":2.32},{"name":"Brunei","area":5765,"population":429646,"populationGrowthRate":1.62},{"name":"Bulgaria","area":110879,"population":7186893,"populationGrowthRate":-0.58},{"name":"Burkina Faso","area":274200,"population":18931686,"populationGrowthRate":3.03},{"name":"Burma","area":676578,"population":56320206,"populationGrowthRate":1.01},{"name":"Burundi","area":27830,"population":10742276,"populationGrowthRate":3.27},{"name":"Cabo 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Islands","area":5,"population":null,"populationGrowthRate":null},{"name":"Sri Lanka","area":65610,"population":22053488,"populationGrowthRate":0.84},{"name":"Sudan","area":1861484,"population":36108853,"populationGrowthRate":1.72},{"name":"Suriname","area":163820,"population":579633,"populationGrowthRate":1.08},{"name":"Svalbard","area":62045,"population":1872,"populationGrowthRate":-0.03},{"name":"Swaziland","area":17364,"population":1435613,"populationGrowthRate":1.11},{"name":"Sweden","area":450295,"population":9801616,"populationGrowthRate":0.8},{"name":"Switzerland","area":41277,"population":8121830,"populationGrowthRate":0.71},{"name":"Syria","area":185180,"population":17064854,"populationGrowthRate":-0.16},{"name":"Taiwan","area":35980,"population":23415126,"populationGrowthRate":0.23},{"name":"Tajikistan","area":143100,"population":8191958,"populationGrowthRate":1.71},{"name":"Tanzania","area":947300,"population":51045882,"populationGrowthRate":2.79},{"name":"Thailand","area":513120,"population":67976405,"populationGrowthRate":0.34},{"name":"Timor-Leste","area":14874,"population":1231116,"populationGrowthRate":2.42},{"name":"Togo","area":56785,"population":7552318,"populationGrowthRate":2.69},{"name":"Trinidad and Tobago","area":5128,"population":1222363,"populationGrowthRate":-0.13},{"name":"Tunisia","area":163610,"population":11037225,"populationGrowthRate":0.89},{"name":"Turkey","area":783562,"population":79414269,"populationGrowthRate":1.26},{"name":"Turkmenistan","area":488100,"population":5231422,"populationGrowthRate":1.14},{"name":"Turks and Caicos Islands","area":948,"population":50280,"populationGrowthRate":2.3},{"name":"Tuvalu","area":26,"population":10869,"populationGrowthRate":0.82},{"name":"Uganda","area":241038,"population":37101745,"populationGrowthRate":3.24},{"name":"Ukraine","area":603550,"population":44429471,"populationGrowthRate":-0.6},{"name":"United Arab Emirates","area":83600,"population":5779760,"populationGrowthRate":2.58},{"name":"United Kingdom","area":243610,"population":64088222,"populationGrowthRate":0.54},{"name":"United States","area":9826675,"population":321368864,"populationGrowthRate":0.78},{"name":"United States Pacific Island Wildlife Refuges","area":22,"population":null,"populationGrowthRate":null},{"name":"Uruguay","area":176215,"population":3341893,"populationGrowthRate":0.27},{"name":"Uzbekistan","area":447400,"population":29199942,"populationGrowthRate":0.93},{"name":"Vanuatu","area":12189,"population":272264,"populationGrowthRate":1.95},{"name":"Venezuela","area":912050,"population":29275460,"populationGrowthRate":1.39},{"name":"Vietnam","area":331210,"population":94348835,"populationGrowthRate":0.97},{"name":"Virgin Islands","area":1910,"population":103574,"populationGrowthRate":-0.59},{"name":"Wake Island","area":7,"population":null,"populationGrowthRate":null},{"name":"Wallis and Futuna","area":142,"population":15613,"populationGrowthRate":0.33},{"name":"West Bank","area":5860,"population":2785366,"populationGrowthRate":1.95},{"name":"Western Sahara","area":266000,"population":570866,"populationGrowthRate":2.82},{"name":"Yemen","area":527968,"population":26737317,"populationGrowthRate":2.47},{"name":"Zambia","area":752618,"population":15066266,"populationGrowthRate":2.88},{"name":"Zimbabwe","area":390757,"population":14229541,"populationGrowthRate":2.21}];
*/


// Logic helpers

// Returns the value at a point in a sorted array. E.g. p = 0.5 -> median
const valueAtPoint = (xs, p) => xs[Math.floor(xs.length * p)];

// Gets the index of an element's quarter in an array
const getQuarter = (xs, x) =>
  x === null                  ? null :
  x <= valueAtPoint(xs, 0.75) ? 0 :
  x <= valueAtPoint(xs, 0.50) ? 1 :
  x <= valueAtPoint(xs, 0.25) ? 2 :
                                3 ;

// Sort numbers largest first, null last
const numericNullLastSorter = (a, b) => 
  a === null ?  1 :
  b === null ? -1 :
  a < b      ?  1 :
  a > b      ? -1 :
                0 ;

// Decorates a sort function to first unwrap property values
const propSorter = (k, f) => (a, b) => f(a[k], b[k]);

// A recursive sort-chainer that keeps on recursing
// until it's either out of sorters, or a sorter has returned
// -1 or 1
const chainSortRec = ([s, ...sorters]) => (a, b) => 
s === undefined ?
  0 :
  s(a, b) || chainSortRec(sorters)(a, b);

// The same sort-chain but implemented as a loop
const chainSort = (sorters) => (a, b) => {
  for (let i = 0; i < sorters.length; i += 1) {
   const res = sorters[i](a, b);
   if (res) return res;
  }    
  return 0;
};

// The main app logic
// props is an array of strings (keys) we want to sort by, in order
// xs is an array of objects that contain those keys
const sortByProps = (props, xs) => {
const og = Symbol();
const quarterProps = props.slice(0, -1)
const numericProp = props[props.length - 1];

// For every property that sortst by quarter,
// we'll need to sort all items to be able to 
// determine the quarter indexes.
const sorts = Object.assign(
  {},
  ...quarterProps.map(k => ({
    [k]: xs
          .map(x => x[k])
          .filter(x => x !== null)
          .sort(numericNullLastSorter)
  }))
);

// We need a place to link the original entries ot the
// values that determine their sort order
const qIndex = xs.map(x => Object.assign(
  // Store a reference to the original item
  { [og]: x },
  // Store the numeric value of the last prop
  { [numericProp]: x[numericProp] },
  // Store the quarter index of the other props
  ...quarterProps.map(k => ({
      [k]: getQuarter(sorts[k], x[k])
  }))
));

// This is our array of sort functions
// Each sort function sorts descending based on a single property
const sorters = props.map(k => propSorter(k, numericNullLastSorter));


return qIndex
  // We sort the index based on all sort methods
  .sort(chainSort(sorters))
  // We return the original objects, not the cached sort values
  .map(x => x[og]);
}



// To format our tests:
const topFiveString = props => sortByProps(props, data)
  .slice(0, 5)
  .map(x => x.name)
  .join(", ");

console.log(

`TOP 5s:
  by area: 
    ${topFiveString(["area"])}
  by area & population: 
    ${topFiveString(["area", "population"])}
  by area, population & growth rate: 
    ${topFiveString(["area", "population", "populationGrowthRate"])}`

);

票数 1

页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持

原文链接：

https://stackoverflow.com/questions/52966025

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